> ## Documentation Index
> Fetch the complete documentation index at: https://docs.vijil.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Custom Harnesses

> Create targeted evaluations with custom Harnesses, personas, and policies.

While Vijil has a variety of pre-configured [Harnesses](/concepts/evaluation-components/harness) that you can select from, you can also create your own Harnesses to obtain a [Trust Score](/concepts/trust-score/introduction) specific to your organization and agent.

## View Custom Harnesses

You can view previously created custom Harnesses by navigating to **Harnesses** in the left sidebar.

To view the prompts, [Personas](/owner-guide/simulate-environment/personas) and [Policies](/owner-guide/simulate-environment/policies) in a custom Harness, click on its row in the **Harnesses** table.

## Create a Custom Harness

1. In the left sidebar, navigate to **Harnesses** and press **Create Harness**.
2. Enter a Harness name and a description.
3. Select an [Agent](/owner-guide/register-agents/what-is-an-agent).
4. <Badge>Optional</Badge> Select one or more [Persona(s)](/owner-guide/simulate-environment/personas).
5. Select one or more [Policies](/owner-guide/simulate-environment/policies).

## Create a Custom Harness via MCP

### Create a Harness

With the [Vijil MCP server](/developer-guide/agentic/quickstart) configured, ask Claude Code in natural language:

<Prompt description="Create a custom Harness called 'Customer Support Harness' for agent a1b2c3d4-… with the GDPR policy">
  Create a custom Harness called 'Customer Support Harness' for agent a1b2c3d4-… with the GDPR policy
</Prompt>

Claude creates the Harness and returns the ID.

<Note>Custom Harnesses are immutable once created. To change the configuration, delete the Harness and create a new one.</Note>

### Check Generation Status

Harness generation is asynchronous. Ask Claude to check until `status` is `active`.

<Prompt description="What is the status of custom Harness h1a2b3c4-…?">
  What is the status of custom Harness h1a2b3c4-…?
</Prompt>

| `status` value               | Meaning                             |
| ---------------------------- | ----------------------------------- |
| `draft` (no workflow)        | Not yet started                     |
| `draft` (workflow `running`) | Generation in progress              |
| `draft` (workflow `failed`)  | Generation failed                   |
| `active`                     | Ready to use in an Evaluation       |
| `failed`                     | Harness creation failed permanently |

### Get Harness Prompts

Retrieve the generated Probes for a completed Harness.

<Prompt description="Show me the prompts for custom Harness h1a2b3c4-…">
  Show me the prompts for custom Harness h1a2b3c4-…
</Prompt>

Returns an empty list if the Harness is still in `draft` status.

### List Custom Harnesses

<Prompt description="List my custom Harnesses">
  List my custom Harnesses
</Prompt>

<Prompt description="List my custom Harnesses for agent a1b2c3d4-… with status active">
  List my custom Harnesses for agent a1b2c3d4-… with status active
</Prompt>

Both support filtering by agent and status.

### Cancel Generation

Stop a Harness that is still generating.

<Prompt description="Cancel the custom Harness h1a2b3c4-… that is still generating">
  Cancel the custom Harness h1a2b3c4-… that is still generating
</Prompt>

### Delete a Harness

<Prompt description="Delete custom Harness h1a2b3c4-…">
  Delete custom Harness h1a2b3c4-…
</Prompt>

## Next Steps

<CardGroup cols={2}>
  <Card title="Run Evaluations" icon="play" href="/owner-guide/run-evaluations/running-evaluations">
    Execute custom Harness evaluations
  </Card>

  <Card title="Understand Results" icon="chart-bar" href="/owner-guide/run-evaluations/understanding-results">
    Analyze custom Harness results
  </Card>

  <Card title="Personas" icon="users" href="/owner-guide/simulate-environment/personas">
    Learn more about Personas
  </Card>

  <Card title="Policies" icon="scroll" href="/owner-guide/simulate-environment/policies">
    Learn more about Policies
  </Card>
</CardGroup>